1. Field of the Invention
The present invention relates to a fuel backflow-preventing device for use in a vehicle. More particularly, the present invention is directed to a fuel backflow-preventing device for preventing injected fuel from being expelled back from the fuel tank due to a rise in the pressure in the fuel tank at the time of supplying fuel to the fuel tank.
2. Description of Related Art
Various types of fuel backflow-preventing devices for use in a vehicle are known in the art. Generally, a fuel tank installed in an automotive vehicle is disposed at a lower part of the vehicle, and the inlet to the fuel tank for supplying fuel thereto is positioned higher than the fuel tank. The fuel that passes through the inlet flows into the fuel tank at a very fast rate which causes the pressure of the air present in the fuel tank to increase by overfilling the fuel tank.
The rise of the pressure inside the fuel tank may cause "burping," a condition whereby small portions of the fuel are expelled back through the filler tube inlet.
A method of preventing "burping" at the time of supplying fuel to a fuel tank is disclosed in U.S. Pat. No. 4,822,054.
As shown in FIG. 1, a conventional fuel backflow-preventing device for use in a vehicle, includes a inlet fuel conduit 31, a pair of guide holes 32 disposed at both sides of the inlet fuel conduit 31, and a cone-shaped floater 34 having a pair of guide plates 33 for slidably engaging with the pair of guide holes, whereby when the fuel volume is small in the fuel tank, the floater 34 descends in the downward direction as shown in FIG. 1 in an actual inlet conduit line. When the fuel volume is increased in the fuel tank, the floater 34 ascends as shown by the dotted line. At this time, although the floater 34 blocks the inlet conduit 31, some fuel will still leak out since it is difficult to tightly block the inlet fuel conduit 31 due to the liquid and vapor pressure from the fuel tank.
In order to avoid these problems, U.S. Pat. No. 5,348,177, which issued to the present inventor, disclosed a fuel backflow-preventing device for use in an automotive vehicle comprising a inlet fuel conduit and a fuel tank; a guide member connected to an inside portion of the inlet fuel conduit having a plurality of slits and a plurality of passages; a floater member having projections slidably engaged in the slits, whereby the floater can rise in the inlet conduit to block the passage in said conduit; and a coupling means for connecting the inside portion of the inlet fuel conduit lengthwise with the guide member.
However, such a conventional fuel backflow-preventing device suffers from a number of problems. For example, the cone-shaped floater cannot tightly block the inlet fuel conduit since the oppositely directed pressure from the inlet fuel conduit is strong. Thus, if the guide holes and guide plates are not in proper alignment, the floater cannot operate to block the inlet fuel conduit. Also, the conventional devices are complicated in structure, expensive to manufacture, and difficult to assemble.